Piper Alpha was a North Seaoil production platform operated by Occidental Petroleum (Caledonia) Ltd.[1] The platform began production in 1976,[2] first as an oil platform and then later converted to gas production. An explosion and the resulting oil and gas fires destroyed it on 6 July 1988, killing 167 men,[3] with only 61 survivors. The death toll included two crewmen of a rescue vessel.[4] The total insured loss was about £1.7 billion (US$3.4 billion). At the time of the disaster, the platform accounted for approximately ten percent of North Sea oil and gas production, and the accident was the worst offshore oil disaster in terms of lives lost and industry impact.[5]

The Kirk of St Nicholas in Union Street, Aberdeen has dedicated a chapel in memory of those who perished and there is a memorial sculpture in the Rose Garden of Hazlehead Park in Aberdeen. Thirty bodies were never recovered.

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Four companies that later transformed into the OPCAL joint venture obtained an oil exploration licence in 1972, discovered the Piper oilfield located at 58°28′N0°15′E﻿ / ﻿58.467°N 0.250°E﻿ / 58.467; 0.250 in early 1973 and commenced fabrication of the platform, pipelines and onshore support structures. Oil production started in 1976 with about 250,000 barrels (40,000 m3) of oil per day increasing to 300,000 barrels (48,000 m3). A gas recovery module was installed by 1980. Production declined to 125,000 barrels (19,900 m3) by 1988. OPCAL built the Flottaoil terminal in the Orkney Islands to receive and process oil from the fields Piper, Claymore and Tartan, each with its own platform. One 30-inch (76 cm) diameter main oil pipeline ran 128 miles (206 km) from Piper Alpha to Flotta, with a short oil pipeline from the Claymore platform joining it some 20 miles (32 km) to the west. The Tartan field also fed oil to Claymore and then onto the main line to Flotta.[6] Separate 18-inch (46 cm) diameter gas pipelines run from Piper to the Tartan platform, and from Piper to the gas compressing platform MCP-01 some 30 miles (48 km) to the northwest.

A large fixed platform, Piper Alpha was situated on the Piper oilfield, approximately 120 miles (193 km) northeast of Aberdeen in 474 feet (144 m) of water, and comprised four modules separated by firewalls.[7] The platform was constructed by McDermott Engineering at Ardersier and UIE at Cherbourg, with the sections united at Ardersier before tow out during 1975, with production commencing in late 1976. For safety reasons the modules were organised so that the most dangerous operations were distant from the personnel areas. The conversion from oil to gas broke this safety concept, with the result that sensitive areas were brought together, for example, the gas compression next to the control room, which played a role in the accident. It produced crude oil and natural gas from 24 wells for delivery to the Flotta oil terminal on Orkney and to other installations by three separate pipelines. At the time of the disaster, Piper was one of the heaviest platforms (along with Magnus and Brae B) operating in the North Sea.

During the late 1970s, major works were carried out to enable the platform to meet UK Government gas export requirements and after this work had been completed, Piper Alpha was operating in what was known as phase 2 mode (operating with the Gas Conservation Module (GCM)) since the end of 1980 up until July 1988; phase 2 mode was its normal operating state. In the late 1980s, major construction, maintenance and upgrade works had been planned by Occidental and by July, 1988, the rig was already well into major work activities, with six major projects identified including the change-out of the GCM unit which meant that the rig had been put back into its initial phase 1 mode (i.e. operating without a GCM unit). Despite the complex and demanding work schedule, Occidental made the decision to continue operating the platform in phase 1 mode throughout this period and not to shut it down, as had been originally planned. The planning and controls that were put in place were thought to be adequate. Therefore Piper continued to export oil at just under 120,000 barrels per day and to export Tartan gas at some 33 MMSCFD (million standard cubic feet per day) during this demanding period.

Because the platform was completely destroyed, and many of those involved died, analysis of events can only suggest a possible chain of events based on known facts. Some witnesses to the events question the official timeline.[8]

12:00 noon Two condensate pumps, designated A and B, displaced the platform's condensate for transport to the coast. On the morning of 6 July, Pump A's pressure safety valve (PSV #504) was removed for routine maintenance. The pump's fortnightly overhaul was planned but had not started. The open condensate pipe was temporarily sealed with a disk cover (flat metal disc also called a blind flange). Because the work could not be completed by 6:00 p.m., the disc cover remained in place. It was hand-tightened only. The on-duty engineer filled in a permit which stated that Pump A was not ready and must not be switched on under any circumstances.

6:00 p.m. The day shift ended, and the night shift started with 62 men running Piper Alpha. As he found the on-duty custodian busy, the engineer neglected to inform him of the condition of Pump A. Instead he placed the permit in the control centre and left. This permit disappeared and was not found. Coincidentally there was another permit issued for the general overhaul of Pump A that had not yet begun.

7:00 p.m. Like many other offshore platforms, Piper Alpha had an automatic fire-fighting system, driven by both diesel and electric pumps (the latter were disabled by the initial explosions). The diesel pumps were designed to suck in large amounts of sea water for fire fighting; the pumps had an automatic control to start them in case of fire (although they could not be remotely started from the control room in an emergency). However, the fire-fighting system was under manual control on the evening of 6 July: the Piper Alpha procedure adopted by the Offshore Installation Manager (OIM) required manual control of the pumps whenever divers were in the water (as they were for approximately 12 hours a day during summer) although in reality, the risk was not seen as significant for divers unless a diver was closer than 10–15 feet from any of the four 120 ft level caged intakes. A recommendation from an earlier audit had suggested that a procedure be developed to keep the pumps in automatic mode if divers were not working in the vicinity of the intakes as was the practice on the Claymore platform, but this was never developed or implemented.[9]

9:45 p.m. Because of problems with the methanol system earlier in the day, Methane clathrate (a flammable ice) had started to accumulate in the gas compression system pipework, causing a blockage. Due to this blockage, condensate (natural gas liquids NGL) Pump B stopped and could not be restarted. As the entire power supply of the offshore construction work depended on this pump, the manager had only a few minutes to bring the pump back online, otherwise the power supply would fail completely. A search was made through the documents to determine whether Condensate Pump A could be started.

9:52 p.m. The permit for the overhaul was found, but not the other permit stating that the pump must not be started under any circumstances due to the missing safety valve. The valve was in a different location from the pump and therefore the permits were stored in different boxes, as they were sorted by location. None of those present were aware that a vital part of the machine had been removed. The manager assumed from the existing documents that it would be safe to start Pump A. The missing valve was not noticed by anyone, particularly as the metal disc replacing the safety valve was several metres above ground level and obscured by machinery.

9:55 p.m. Condensate Pump A was switched on. Gas flowed into the pump, and because of the missing safety valve, produced an overpressure which the loosely fitted metal disc did not withstand.[10]

Gas audibly leaked out at high pressure, drawing the attention of several men and triggering six gas alarms including the high level gas alarm. Before anyone could act, the gas ignited and exploded, blowing through the firewall made up of 2.5 × 1.5 metre panels bolted together, which were not designed to withstand explosions. The custodian pressed the emergency stop button, closing huge valves in the sea lines and ceasing all oil and gas production.

Theoretically, the platform would then have been isolated from the flow of oil and gas and the fire contained. However, because the platform was originally built for oil, the firewalls were designed to resist fire rather than withstand explosions. The first explosion broke the firewall and dislodged panels around Module (B). One of the flying panels ruptured a small condensate pipe, creating another fire.

10:04 p.m. The control room was abandoned. Piper Alpha's design made no allowances for the destruction of the control room, and the platform's organisation disintegrated. No attempt was made to use loudspeakers or to order an evacuation.

Emergency procedures instructed personnel to make their way to lifeboat stations, but the fire prevented them from doing so. Instead the men moved to the fireproofed accommodation block beneath the helicopter deck to await further instructions. Wind, fire and smoke prevented helicopter landings and no further instructions were given, with smoke beginning to penetrate the personnel block.

As the crisis mounted, two men donned protective gear and attempted to reach the diesel pumping machinery below decks and activate the firefighting system. They were never seen again.

The fire would have burnt out were it not being fed with oil from both Tartan and the Claymore platforms, the resulting back pressure forcing fresh fuel out of ruptured pipework on Piper, directly into the heart of the fire. The Claymore platform continued pumping until the second explosion because the manager had no permission from the Occidental control centre to shut down. Also, the connecting pipeline to Tartan continued to pump, as its manager had been directed by his superior. The reason for this procedure was the huge cost of such a shut down. It would have taken several days to restart production after a stop, with substantial financial consequences.

Gas pipelines of both 16″ and 18″ diameter ran to Piper Alpha. Two years earlier Occidental management ordered a study, the results of which warned of the dangers of these gas lines. Because of their length and diameter, it would have taken several hours to reduce their pressure, so that it would not have been possible to fight a fire fuelled by them. Although the management admitted how devastating a gas explosion would be, Claymore and Tartan were not switched off with the first emergency call.

10:20 p.m. Tartan's gas line (pressurised to 120 Atmospheres) melted and burst, releasing 15-30 tonnes of gas every second, which immediately ignited. From that moment on, the platform's destruction was assured.

10:30 p.m. The Tharos, a large semi-submersible fire fighting, rescue and accommodation vessel, drew alongside Piper Alpha. The Tharos used its water cannon where it could, but it was restricted, because the cannon were so powerful they would injure or kill anyone hit by the water.

10:50 p.m. The second gas line ruptured (the riser for the MCP-01 platform), ejecting millions of cubic feet of gas into the conflagration. Huge flames shot over 300 ft (90 m) in the air. The Tharos was driven off by the fearsome heat, which began to melt the surrounding machinery and steelwork. It was only after this second explosion that the Claymore platform stopped pumping oil. Personnel still left alive were either desperately sheltering in the scorched, smoke-filled accommodation block or leaping from the various deck levels, including the helideck, some 175 ft (50 m) into the North Sea. The explosion also killed two crewmen on a fast rescue boat launched from the standby vessel Sandhaven and the six Piper Alpha crewmen they had rescued from the water.[4]

There is controversy about whether there was sufficient time for more effective emergency evacuation. The main problem was that most of the personnel who had the authority to order evacuation had been killed when the first explosion destroyed the control room. This was a consequence of the platform design, including the absence of blast walls. Another contributing factor was that the nearby connected platforms Tartan and Claymore continued to pump gas and oil to Piper Alpha until its pipeline ruptured in the heat in the second explosion. Their operations crews did not believe they had authority to shut off production, even though they could see that Piper Alpha was burning.[12]

The nearby diving support vessel Lowland Cavalier reported the initial explosion just before 10:00 pm, and the second explosion occurred twenty two minutes later. By the time civil and military rescue helicopters reached the scene, flames over 100 metres in height and visible as far away as 100 km (120 km from the Maersk Highlander) away prevented safe approach. The largest number of survivors (37 out of 59) were recovered by the Fast Rescue Craft MV Silver Pit; coxswain James Clark later received the George Medal. Others awarded the George Medal were Charles Haffey from Methil [1], Andrew Kiloh from Aberdeen, and James McNeill from Oban [2][3].

The blazing remains of the platform were eventually extinguished three weeks later by a team led by firefighter Red Adair, despite reported conditions of 80 mph (130 km/h) winds and 70-foot (20 m) waves.[13] The part of the platform which contained the galley where about 100 victims had taken refuge was recovered in late 1988 from the sea bed, and the bodies of 87 men were found inside.[4]

The Piper Alpha Window, Ferryhill Church, Aberdeen, created by Jennifer Jane Bayliss, a member of the congregation. Each of the small circular discs represents a victim of the disaster. At the foot of the window they are red, as the souls of the dead emerge from the flames in the stormy sea. As they rise up the window the colour lightens as the souls rise to Heaven

The Cullen Inquiry was set up in November 1988 to establish the cause of the disaster. It was chaired by the Scottish judge William Cullen. After 180 days of proceedings,[14] it released its report Public Inquiry into the Piper Alpha Disaster (short: Cullen Report) in November 1990.[15] It concluded that the initial condensate leak was the result of maintenance work being carried out simultaneously on a pump and related safety valve. The inquiry was critical of Piper Alpha's operator, Occidental, which was found guilty of having inadequate maintenance and safety procedures, but no criminal charges were ever brought against the company.[4]

The second part of the report made 106 recommendations for changes to North Sea safety procedures:

37 recommendations covered procedures for operating equipment, 32 the information of platform personnel, 25 the design of platforms and 12 the information of emergency services[16]

The responsibility to implement was for 57 with the regulator, 40 for the operators, 8 for the industry as a whole and 1 for stand-by ship owners.[17]

Most significant of these recommendations was that operators were required to present a safety case and that the responsibility for enforcing safety in the North Sea should be moved from the Department of Energy to the Health and Safety Executive, as having both production and safety overseen by the same agency was a conflict of interest.[20]

The disaster led to insurance claims of around $1.4 billion USD, making it at that time the largest insured man-made catastrophe. The insurance and reinsurance claims process revealed serious weaknesses in the way insurers at Lloyd's of London and elsewhere kept track of their potential exposures, and led to their procedures being reformed.[21]

Survivors and relatives of those who died went on to form the Piper Alpha Families and Survivors Association, which campaigns on North Sea safety issues.[22] The wreck buoy marking the remains of the Piper is approximately 1.1 nautical miles from the replacement Piper Bravo platform. A lasting effect of the Piper Alpha disaster was the establishment of Britain's first "post-Margaret Thatcher" trade union, the Offshore Industry Liaison Committee.

A memorial sculpture, showing three oil workers, was erected in the Rose Garden within Hazlehead Park in Aberdeen.[23] The figures represent on the west the physical nature of offshore trades, the east youth and eternal movement and the north holds an unwinding spiral that represents oil in the left hand.[24] The sculptor is Sue Jane Taylor, the Scottish artist who had visited the Piper platform the previous year, and based much of her work around what she saw in and around the oil industry. In 1991, Scottish composer James MacMillan wrote "Tuireadh", a piece for clarinet and string orchestra, as a musical complement to the memorial sculpture. In 2008, to mark the 20th anniversary of the disaster, a stage play, Lest We Forget was commissioned by Aberdeen Performing Arts and written by playwright Mike Gibb . It was performed in Aberdeen, Scotland in the week leading up to the anniversary with the final performance on 6 July 2008, twenty years to the day.[25]

Beginning in 1998, one month after the tenth anniversary, Professor David Alexander, director of the Aberdeen Centre for Trauma Research at Robert Gordon University carried out a study into the long-term psychological and social effects of Piper Alpha. He managed to find thirty-six survivors who agreed to give interviews or complete questionnaires. Almost all of this group reported psychological problems. More than 70% of those interviewed reported psychological and behavioural symptoms of post traumatic stress disorder. Twenty-eight said they had difficulty in finding employment following the disaster; it appears that some offshore employers regarded Piper Alpha survivors as Jonahs – bringers of bad luck, who would not be welcome on other rigs and platforms. The family members of the dead and surviving victims also reported various psychological and social problems. Alexander also wrote that "some of these lads are stronger than before Piper. They've learned things about themselves, changed their values, some relationships became stronger. People realised they have strengths they didn't know they had. There was a lot of heroism took place."[4]

In 2013, on the 25th anniversary of the disaster, the video Remembering Piper - The Night That Changed Our Lives was released by Step Change in Safety.[26] A three-day conference was held in Aberdeen to reflect on lessons learned from Piper Alpha and industry safety issues in general.[27][28]

^Cullen, The Hon. Lord William Douglas (November 1990). The Public Inquiry into the Piper Alpha Disaster, Presented to Parliament by the Secretary of State for Energy by Command of Her Majesty. London: H.M. Stationery Office. ISBN0101113102. OCLC23102869. 488 pages, 2 volumes